Evaluation of the normal values for signal-averaged electrocardiogram.

摘要

Late potentials are low-amplitude wave forms within the terminal portion of the QRS complex. They can be recorded as a signal-averaged electrocardiogram. Late potentials indicate slow conduction within the ventricular myocardium that can be a substrate for arrhythmogenesis. It is surprising that the definition of a positive signal-averaged ECG is not standardized. Criteria for normal values for a SAECG are those published in 1991 and 1996 in the Journal of the American College of Cardiology for risk stratification in postinfarction patients. Usually, 300-400 beats are averaged to meet the criteria of a noise level <0.3 muM. In these publications, it was suggested that for 40 Hz high-pass filtering, the normal value for filtered QRS (fQRS) duration is < 114 msec, the normal value of low-amplitude signal duration below 40 muV (LAS 40) is <38 msec, and the root-mean square voltage in the last 40 msec of the QRS (RMS 40) should be >20 muV. It has become common practice to state that the SAECG is positive if two of the three parameters are abnormal, although this categorization is not based on evidence.